(a) Field of the Invention
The present invention relates to a thin film panel, a driving device, and a liquid crystal display having the same. More particularly, the present invention relates to a thin film panel and a driving device fitted with an illumination sensor having a spectrum property that is close to human visibility, and a liquid crystal display having the same.
(b) Description of the Related Art
Generally, a liquid crystal display (“LCD”) includes a lower panel having pixel electrodes and an upper panel having a common electrode, and a liquid crystal layer having dielectric anisotropy therebetween. The lower panel includes a plurality of gate lines and data lines forming pixel areas. The pixel electrodes are arranged in a matrix shape within the pixel areas, are connected to switching elements such as thin film transistors (“TFTs”), and are supplied with data voltages line by line. The common electrode is formed on the entire surface of the upper panel and is supplied with a common voltage. The liquid crystal layer between the pixel electrodes and the common electrode constitutes a liquid crystal capacitor from the viewpoint of circuitry, and the liquid crystal capacitor forms a basic unit of a pixel along with a switching element, such as a TFT, connected to the liquid crystal capacitor.
In such an LCD, a desired image can be obtained by applying voltages to the pixel and common electrodes to generate an electric field in the liquid crystal layer and by adjusting the intensity of the electric field to control the transmittivity of light passing through the liquid crystal layer.
The light may be emitted from an artificial light source specifically provided or it may be natural light.
The light source unit for the LCD, that is, a backlight unit, employs a plurality of fluorescent lamps such as a cold cathode fluorescent lamp (“CCFL”) or an external electrode fluorescent lamp (“EEFL”) as a light source, and includes inverters for driving the lamps. The inverter turns on a lamp by converting an input DC voltage into an AC voltage in response to a brightness control voltage inputted from an external device and applying the AC voltage to the lamp. The inverter also adjusts the brightness of the lamp, detects current flowing in the lamp, and controls the voltage applied to the lamp on the basis of the detected current.
Such an LCD can be classified into a transmissive LCD, a reflective LCD, and a transflective LCD. The transmissive LCD displays an image by the use of a lighting unit disposed on the rear surface of a liquid crystal panel assembly. The reflective LCD displays an image by the use of external natural light. The transflective LCD has a structure in which the transmissive LCD and the reflective LCD are combined structurally. The transflective LCD operates in a transmission mode in which an image is displayed by the use of an internal light source indoors or in a dark place where no external light source exists, and operates in a reflection mode in which an image is displayed by reflecting external light outdoors or in a bright place, depending upon the types of light source.
As for an LCD such as an LCD television, technologies for realizing optimal image quality by varying screen brightness in response to ambient illumination have been developed. For example, company S advertises that by providing an external illumination sensor to the outside of an LCD and adjusting a backlight depending upon an indoor light status, the LCD televisions made by the company S should maintain the optimal brightness and image quality even when the indoor lighting status varies or the LCD televisions are placed by a window through which a lot of external natural light enters.
In a bright indoor place, that is, in an indoor place with high illumination, such an LCD television maximizes the brightness of the backlight and provides a vivid screen, while in a dark indoor place, that is, in an indoor place with low illumination, the LCD television provides too bright a screen such that human eyes become tired and a phenomenon that dark colors become bright colors to reduce a contrast ratio occurs. This is because the light intensity of the backlight is too great which causes the leakage of light to increase.
The conventional external-fitting illumination sensor used for solving such a problem detects only incident light energy regardless of spectrums of light sources. That is, the conventional external-fitting illumination sensor does not distinguish the kinds or types of light sources from each other, though the light source may be natural light such as daylight and may be fluorescent light or candescent light.
In order to solve such a problem, a sensor characteristic to be closer to the human visibility by changing the structure of the illumination sensor or inserting an optical filter thereto is needed, however, there is a problem in that change of elements and addition of processes for purchasing and fitting such a sensor increase cost.